1. Field
The present disclosure relates to Fibre Channel networks. More specifically, the present disclosure relates to a method and apparatus for managing network congestion in a Fibre Channel network.
2. Related Art
The proliferation of the Internet and e-commerce continues to fuel revolutionary changes in the network industry. Today, a significant number of transactions, from real-time stock trades to retail sales, auction bids, and credit-card payments, are conducted online. Consequently, many enterprises rely on existing storage area networks (SANs), not only to perform conventional storage functions such as data backup, but also to carry out an increasing number of egalitarian network functions such as building large server farms.
A predominant form of SAN is the Fibre Channel (FC) network. FC standards were developed based on High Performance Parallel Interface (HIPPI), a data channel standard developed by Los Alamos National Laboratory in the 1980's. HIPPI was designed as a supercomputer I/O interface with high throughput and minimal switching function. As time went on, optical fiber became cheaper and more reliable, and FC was developed as a successor to HIPPI to take advantage of the high capacity of fiber optics. FC can carry data channels including HIPPI, Small Computer Systems Interface (SCSI), and multiplexor channels used on mainframes, as well as network traffic, including IEEE 802, Internet Protocol (IP), and Asynchronous Transfer Mode (ATM) packets. Like HIPPI, the basic topology of an FC network is a star topology with a switch fabric at the center to connect inputs to outputs.
Historically, conventional network appliances (e.g., data-center servers, disk arrays, backup tape drives) mainly use an FC network to transfer large blocks of data. Therefore, FC switches provide only basic patch-panel-like functions. In the past decade, however, drastic advances occurred in almost all the network layers, ranging from the physical transmission media, computer hardware and architecture, to operating system (OS) and application software.
For example, a single-wavelength channel in an optical fiber can provide 10 Gbps of transmission capacity. With wavelength-division-multiplexing (WDM) technology, a single strand of fiber can provide 40, 80, or 160 Gbps aggregate capacity. Meanwhile, computer hardware is becoming progressively cheaper and faster. Expensive high-end servers can now be readily replaced by a farm of many smaller, cheaper, and equally fast computers. In addition, OS technologies, such as virtual machines, have unleashed the power of fast hardware and provide an unprecedented versatile computing environment.
As a result of these technological advances, an FC switch fabric faces a much more heterogeneous, versatile, and dynamic environment. The port count on a switch fabric is becoming progressively larger, and its topology increasingly more complex. Conventionally, FC switches and host bus adaptors do not have any congestion-management mechanisms. However, as the edge devices' injection data rate continues to grow and more data flows traverse multiple switches in the fabric, network congestion is more likely to occur in an FC network. Congestion can impair network performance, and severe congestion can even cause the network to collapse.